Development of a High Performance Thermal Interface Material With Vertically Aligned Graphite Platelets

Abstract

This paper introduces a high performance thermal interface material (TIM) with vertically aligned graphite. The main structure of the TIM is a vertically laminated structure, in which thin solder layers are laminated with aligned graphite layers. Unlike traditional TIMs infiltrated with randomly oriented high conductive fillers, the laminated TIM with vertically aligned graphite provides extraordinarily high z-axis thermal conductivity and controllable stiffness by simply setting the thickness of each component layer to match different surfaces. Thus, this design greatly improves the overall heat transfer performance. In addition, using metallic-graphite composites greatly improves the bonding between the graphite and the metallic host compared to nonmetallic materials, and thus the thermal boundary resistance can be significantly reduced. Moreover, compared to organic hosts, solders have much smaller phonon spectra mismatch with graphite nanoplatelets (GNPs), and thus offer significantly higher interface conductance. Furthermore, vertically connected solder layers can also lock the graphite layers in place and reinforce the strength of the entire package. A series of experimental tests was conducted to evaluate the effects of processing pressure and surface roughness on the overall thermal performance of the graphite TIMs. The results indicated that the overall thermal resistance of two smooth surfaces soldered by a 200 μm-thick graphite TIM was reduced from 0.12 to 0.03 cm2•K/W when the compression pressure applied during the soldering process was increased from 7 to 68 psi. Increased surface roughness appeared to improve heat transfer across the interface by enlarging the contact areas between the surface and the graphite TIMs. A preliminary numerical simulation verified this trend.

Advanced thermal management technologies for defense electronics

“…A selected bibliography of NTI team publications is included in this paper [31][32][33][34][35][36][37].…”

Thermal performance and reliability characterization of bonded interface materials (BIMs)

“…This allows the process to engineer the desired shear and compressive compliance within the interface while also optimizing for minimal thermal resistance. Teledyne developed a bonding process that vertically aligns graphite platelets within the contact area between two surfaces [14]. The platelets are first aligned and compressed into thin layers before a solder binds the graphite layers to each other and to the surfaces.…”

Towards Embedded Cooling - Gen 3 Thermal Packaging Technology

“…The GLAD copper springs (GE) and graphite-solder laminated structures (Teledyne) showed the lowest resistivities and are currently undergoing aging and temperature cycling tests to establish their robustness and durability. A selected bibliography of NTI team publications is included in this paper [37][38][39][40][41][42][43][44].…”